In certain devices, reagents are delivered to produce a reaction product monitored by sensors. However, there are currently no adequate solutions that allow for efficient storage and transportation of reagents that also limit user handling and interaction, including potential contamination, in preparation of the mixed reagents. Thorough and consistent mixing of a reagent in solution is also desirable. In view of the above, it would be advantageous to have a device for preparing a reagent solution which overcame the deficiencies of current approaches.